Glass offers an improved means of storing nuclear waste, researchers have found.
University of Sheffield researchers have shown that glass could be a better method for long-term storage, transport and disposal of Intermediate Level Waste (ILW).
ILW makes up more than three quarters of the volume of material destined for geological disposal in the UK.
The UK’s preferred method is to encapsulate ILW in specially-formulated cement. The waste is mixed with cement and sealed in steel drums, in preparation for disposal deep underground.
But studies have found that turning this kind of waste into glass, a process called vitrification, could be a better method for its eventual disposal.
The research programme, funded by the UK’s NDA and led by Professor Neil Hyatt in the Department of Materials Science and Engineering at the University of Sheffield, tested simulated radioactive waste materials – those with the same chemical and physical makeup, but with non-radioactive isotopes – to produce glass and assess its suitability for storing lower grades of nuclear waste.
The process used to produce the glass waste storage packages is straightforward: the waste is dried, mixed with glass forming materials such as iron oxide or sodium carbonate, heated to make glass and finally poured into a container.
For certain wastes such as radioactively contaminated sand the waste is actually used in the glassmaking process.
A key discovery made by the Sheffield team was that the glasses produced for ILW proved to be very resistant to damage by energetic gamma rays, produced from the decay of radioactive materials.
"We found that gamma irradiation produced no change in the physical properties of these glasses, and no evidence that the residual radiation caused defects,” said Professor Hyatt.
“We think this is due to the presence of iron in the glass, which helps heal any defects so they cannot damage the material.
"For large volumes of waste that need to be stored securely, then transported to and eventually disposed of, vitrification could offer improved safety and cost effectiveness," said Professor Hyatt.
